Much effort has been expended attempting to develop gene therapy based treatments for many inherited diseases. Progress toward this end has been hampered by an inability to transfer cDNA versions of genes into cells and have their expression regulated properly. The studies described herein propose to evaluate a fundamentally different approach to gene therapy that is based upon ribozyme-mediated repair of mutant RNAs. For many genetic diseases, this novel approach may be more useful that the conventional "gene add back" approach to gene therapy because RNA repair should restore the regulated expression of mutant genes, by repairing the mutant RNAs only when they are present, and simultaneously eliminate the production of mutant proteins. Sickle cell disease is an ideal genetic disorder to focus on to begin to explore the potential utility of RNA repair. Repair of sickle beta-globin transcripts could simultaneously engender the regulated production of normal beta-globin while reducing sickle beta-globin levels. In addition, because expression of the beta-globin gene is highly regulated, it has been difficult to develop traditional gene therapy approaches for the treatment of sickle cell disease. Therefore, the objectives of this study are: 1.) To map sickle beta-globin transcripts to determine which regions of the RNA are accessible to trans-splicing ribozymes. 2.) To create trans-splicing ribozymes based upon the Tetrahymena group I intron that can repair sickle beta-globin transcripts and test their activity in vitro. 3.) To determine if repair of sickle beta-globin transcripts can proceed in tissue culture cells when the ribozyme and sickle beta-globin RNAs are transiently expressed. 4.) To determine if trans-splicing ribozymes can repair sickle beta-globin mRNAs and engender normal beta-globin production in a cell line harboring a Sickle beta-globin gene. 5.) To monitor the efficiency of sickle beta-globin RNA repair in these cell systems and improve the efficiency of repair if required.